Trucks and trains are often used to transport goods over long distances. When transported this way, goods are often placed in freight storage containers. Because of the nature of the trip, which may take many days to complete, shipments of goods are often left unattended at some time before reaching their final destination. To protect the goods from theft, the storage container may be locked shut.
At one time, padlocks and combination locks were sufficient to lock storage containers. However, as truck and rail shipping grew in popularity, logistics and security-related issues rendered those types of locks insufficient, if not inappropriate. As shipping routes became more complex, goods were transported to remote destinations, with partial deliveries and pickups made along the way. As a result, more people handled a container before it reached its final destination. Padlocks and combination locks were logistical nightmares: because the locks were too expensive to merely destroy at each stop, each person who needed to access the container also needed access to the key or combination. Besides creating logistical concerns, these locks created accountability problems, as well: a padlock or combination lock could be completely cut off and replaced without any indication of the replacement. This meant that goods could be stolen without a shipper's knowledge. A container that had been robbed and re-secured might leave the scene of the crime before the goods or thief could be found. And because many shippers might handle a container before it reached its destination, blame for lost goods was difficult to assess. These logistical and accountability-based problems prompted use of alternate sealing devices.
Seals were designed to avoid the logistical and accountability problems. Often these designs used brittle materials which cracked or shattered when an attempt was made to defeat the seal. Other types of seals were constructed with alternating layers of high-contrast materials which gave visual indication that the surface of the seal had been abused. Alas, these seals provided a barrier that was more psychological than physical. In other words, these were highly visible and often deterred "conscientious" thieves. Unfortunately, these "tamper-indicating" seals would not protect goods from theft by determined criminals. These seals were not sufficient.
Accordingly, new, more-rugged seals were created. However, while these new seals provided improved security, they were troublesome in their own right. As seals were created with more structural integrity, their application often required the use of tools. For example, U.S. Pat. No. 3,862,775 discloses a seal which has a portion that must be permanently deformed by the user. These seals were too hard to use.
Other seals were designed to provide security without the use of tools. To accomplish this, many seals comprised various dedicated parts which the user combined to create a container seal. For example, U.S. Pat. No. 4,592,579 discloses a seal having a barrel that slides onto a segmented insert that has passed through hasps on a pair of container doors. This type of seal often eliminated the need for tools, but created a new problem: if one component was missing, the others were essentially useless. In order to use large numbers of these multi-component seals efficiently, careful inventory of the individual parts had to be kept. If a user ran short of one component, the seal could not be applied correctly. Ultimately, these seals created the logistical problems that existed with padlocks and combination locks.
Accordingly, what is needed is a locking device for sealing containers that is inexpensive, disposable, applied without tools, and designed to indicate unauthorized entry into a container.